Clutch systems are used in motor vehicles for separating the engine and gearbox. In modern vehicles, virtually exclusive use is made of friction clutches or hydrodynamic transmissions. In the customary friction clutch, force-transmitting connection between the shaft from the engine and the shaft entering the gearbox is established by means of one or more disks pressed against one another, with at least one clutch disk connected to the shaft entering the gearbox, which has linings on both sides, being located between the flywheel of the engine and a clutch pressure plate. When the clutch pedal is depressed, the pressure plate is pushed away from the clutch disk against the spring force of the disk spring, as a result of which the clutch disk is released. The connection between the engine and the gearbox is thereby interrupted.
The magnitude of the torque which can be transmitted depends on the area and the diameter of the clutch disk and on the spring force of the disk spring. For large torques, clutch systems having a relatively large friction area or multidisk clutches are therefore used. The clutch disk is, especially on starting, subject to wear by rubbing and is heated by the friction.
In view of this prior art, it is an object of the invention to provide clutch systems which can transmit large torques at small construction sizes. Single-disk systems which have relatively small friction areas are preferred for this purpose.
Friction pairings with ceramic materials, in particular fiber-reinforced ceramic materials, are known. When used as brake disks, high heat resistance and a coefficient of friction which has a low dependence on the load are required. In the case of clutch systems, high static friction and high torsional stiffness are desired.
In EP-A 0 866 923, a friction pairing for clutches is disclosed which comprises a network of carbon fibers, with silicon carbide being present in the filler. The silicon carbide is obtained by reaction of the free carbon present in the network which is not in fiber form with a silicon melt. The fiber network is always also attacked in this reaction unless recourse is made to particular measures for protecting the fibers, as described, for example, in DE-A 197 10 105, and these measures considerably increase the costs of producing the fibers protected in this way.